Swimming Pool Pump Motors: At the Heart of Your Pool’s Cleanliness

• Home
• Pools & Spas: Build Your Dream Pool
• Privacy
• Contact

Swimming Pool Pump Motors: At the Heart of Your Pool’s Cleanliness

Tuesday, June 17th, 2008    Subscribe To Our Feed

What happens when your swimming pool pump motor dies? Well, I found out a little over three weeks ago. Truth be told, it was on death watch for weeks before that. A bad storm came through months ago, blew lots of tree branches and debris into the yard and pool and produced massive lightning that shorted the pump. As it was way past pool season, hubby and I didn’t really care much at the time. It worked, but made terrible screeching and rattling sounds - “the death rattle”, we’d joke, as we fished for limbs in the pool’s deep end.

Well, opening the pool this year has been h*ll.  There’s new construction in back of the house, and dust and new debris constantly blows through the yard and, of course, into the pool. Wanna manually vacuum Georgia red clay out of your swimming pool? It ain’t fun. My cartridge filters are begging for mercy. The pool pump got slower and harder to start until it finally quit. We were gone for a weekend, and came back to a ominously cloudy pool. We’ve decided to replace it with the same model swimming pool pump. Of course, no one has that pump in stock, it has to be special ordered, and there’s a three week wait for service thanks to pool opening season being in full swing. No, not even the local Leslie’s Pool Supply had it (!). Seems it’s a pretty fancy model I inherited - a 2.5 HP Hayward Super II two-speed pump - that I understand isn’t usually stocked in the back room.

So I’ve been manually adding chlorine shock to my swimming pool these past weeks in a slowly failing effort to keep 30,000 gallons of clay laden H2O from turning green under 90+ degree heat. These woes, plus a bout of ill health, make for a lousy start to summer.  As swimming pool pump motors and researching them are at the top of my mind, thought I’d post a bit about them.

The swimming pool pump motor can be considered as the beating heart of your pool’s filtration and sanitization system.  As I can personally attest, any still body of water sitting outdoors in hot weather becomes a steaming soup of algae PDQ. The pump is necessary to move your pool’s water through the filters to sift out debris (like bugs and clay silt) and in my pool’s case through the salt system cell that converts the salt in my water to chlorine and through the gas heater for cooler fall evenings. My auto pool cleaner also runs off the pool pump motor (happy, happy joy…) so if the pump is out, my beautiful salt water swimming pool is effectively DOA.

Swimming Pool Pump Sizing
When it comes to choosing a pool pump, bigger is NOT necessarily better and horsepower is not always what it’s hyped up to be. When replacing a swimming pool pump motor a real constraint is the size of your filter system and the pipes. A pump that is too big and powerful can blow out your pipes and damage your filter and heater with the force of the water. It’s safe, and generally recommended, to match what you already have; which is what I’m doing.

If you’re replacing your filter system along with your pump, by all means look into a different size. There’s no way to know if the builder sized the pool pump properly from the beginning. Oversized swimming pool pumps can consume lots of electricity needlessly; too-small pumps won’t keep your water as sparkling as it should be. So it may pay to question if you need to change pump sizes.

First, you want a pump that can circulate all the water in the pool through the filters within 8 - 12 hours. This is called the “turnover time”. The more use your pool gets, the shorter the turnover time needs to be. For summer’s typically heavy use, you may want to look at times between 8 and 10 hours. [Sidebar: In my case, the swimming pool pump I have is big (so are my filters) and there’s not many of us here to use the pool daily; 4 - 6 hours has usually been fine for me and mine, but YMMV. Now with all the dust; or if I have guests, I must ramp up accordingly.] Divide the total number of gallons of water in your pool by the desired turnover time; then divide the result by 60 (minutes) to get the minimum flow rate (measured in gallons per minute, or GPM).

You also want to check the maximum flow rate, which is determined by a combination of the size of your pipes and the design flow rating (measured in GPM) of your filtration system. Obviously a larger sized pipe, say 2 inches in diameter can carry more water and will have a higher flow capacity than a smaller 1 1/2 inch pipe.  A typical 1 1/2 inch pipe has a maximum flow of about 42 GPM. A 2 inch pipe has roughly a 73 GPM maximum flow. By counting the number of intake lines into the pump and multiplying this by the maximum flow rate of the pipe, this will tell you what the maximum flow into the pump will be. So if you have two 2 inch intake lines going to the pump, each rated at 73 GPM, the flow into the pump will be 146 GPM. Pool filter manufacturers have performance data charts that will give you the flow rating for specific filter models.

Basically you want to choose a swimming pool pump whose power to move water (as measured in GPM) does not exceed either the flow capacity of the intake pipes or the design flow rating of your filter system; and still has the power to turn over all your pool water within the desired 8 - 12 hours. You can see why a swimming pool pump motor that’s too powerful can strain and damage your system, wasting electricity in the process; while an undersized pump will never fully clean your pool.

Swimming pool pumps for above-ground pools are different than those for in-ground pools. You may hear terms like ”low head pump”, “high head pump”; or “feet of head”. The technicalities are really too complex for this humble blogger to fully explain here. I’ll try to briefly sum what I’ve learned.

Technically, feet of head is a measure of the swimming pool pump motor’s energy output. A pump that produces 50 feet of head is capable of propelling any liquid - water, oil, molasses - regardless of density or thickness 50 feet high into the air.  In a rough sort of way, “feet of head” might also be thought of as a measure of flowrate. Why is this important? Your swimming pool’s water travels through lengths of piping, whether above or below ground, to get to the filtration system. The longer the distance the water must travel to your pool’s sanitation, the more energy is needed to pull that water through the piping and into the filters. An above-ground pool typically requires somewhat less energy to pull water to the filter because the filtration system is located close to the pool so there’s less pipe (less distance) for the water to travel and usually less equipment attached such as heaters and spas. Above-ground pools generally use low-head pumps. An inground pool generally requires more energy to pull water to and through the filters because of longer pipe runs and more attached features; therefore they use medium-head or high-head pumps. Got it?

Note again that this doesn’t necessarily correlate to horsepower. I understand it’s possible to have a 3/4 hp pump that has the same flowrate, or produces the same output measured in feet of head, as a 1.5 hp pump motor. But the 3/4 hp motor will use less electricity, reducing your monthly bill. Lower swimming pool energy consumption is environmentally friendly. Two-speed and multi-speed pumps are also available that can be adjusted or programmed according to needs. There are flow rate charts, available from the swimming pool pump manufacturers and supply houses, that can help you choose the properly rated pump. Calculating feet of head is not for the faint of math. If you have ANY questions or doubts about your choices, please consult your local pool professional. Please don’t ask me! Hayward pool pumps, Pentair pumps, Sta-Rite and Jandy are well-known and respected brands for the residential market.

I’m still waiting for my replacement pump to arrive and my twice-weekly chores to be over (sob!). But I hope this discussion about swimming pool pump motors helps you in choosing the right pump for your pool.

One Response to “Swimming Pool Pump Motors: At the Heart of Your Pool’s Cleanliness”

1. Above Ground » Swimming Pool Pump Motors: At the Heart of Your Pool’s Cleanliness Says:
   June 17th, 2008 at 3:58 pm

   […] swimming pool pump motors: At the Heart of Your Pool’s Cleanliness swimming pool pump motors: At the Heart of Your Pool’s Cleanliness June 17th, 2008 Subscribe To Our Feed What happens when your swimming pool pump motor dies? Well, I found out a little over three weeks ago. Truth be told, it was on death watch for weeks before that. A bad storm came through months ago, blew lots of tree branches and debris into the yard and pool and produced massive lightning that shorted the pump. As it was way past pool season, hubby and I didn’t really care much at th […]

Copyright © 2007 - 2009 THE Swimming Pool Resource Blog